Such a circuit is known from the general state of the art as shown in FIG. 1. The known circuit comprises an amplifier AMP having a differential input 5;6 comprising an input node 5 and an input node 6, and a differential output 7;8 comprising an output node 7 and an output node 8. The circuit further comprises an input chopper CHPi arranged in cascade in between a differential input 1;2 of the circuit and the differential input 5;6 of the amplifier AMP, and an output chopper CHPo synchronised with the input chopper CHPi, which output chopper CHPo is arranged in cascade in between the differential output 7;8 of the amplifier AMP and a differential output 3;4 of the circuit. The operation of the known circuit is as follows. An input signal Vin is supplied to the differential input 1;2. In response to the input signal Vin an output signal Vout is delivered to the differential output 3;4. The input chopper CHPi is arranged for alternately coupling either input terminals 1 and 2 of the differential input 1;2 to respectively input nodes 5 and 6 of the differential input 5;6 during a first phase PHi1, or input terminals 1 and 2 of the differential input 1;2 to respectively input nodes 6 and 5 of the differential input 5;6 during a second phase PHI2. The output chopper CHPo is arranged for alternately coupling either output nodes 7 and 8 of the differential output 7;8 to respectively output terminals 3 and 4 of the differential output 3;4 during a first phase PHi1, or output nodes 7 and 8 of the differential output 7;8 to respectively output terminals 4 and 3 of the differential output 3;4 during a second phase PHI2. The input signal Vin is converted to the output signal Vout in virtually the same manner as in the case that the input chopper CHPi and the output chopper CHPo would not have been present. However by the presence of the input chopper CHPi and the output chopper CHPo the offset produced by the amplifier AMP, which offset is denoted as Vos in FIG. 1, is eliminated. Also the noise produced by the amplifier AMP is significantly reduced for frequencies lower than the switching frequency of the switches in the input chopper CHPi and the output chopper CHPo. For the purpose of reducing the noise produced by the amplifier AMP the aforementioned switching frequency must be as high as possible.
A problem of the known circuit is that for a high switching frequency the so-called charge injection caused by the switches of the input chopper CHPi and the output chopper CHPo causes a DC-offset in the output signal Vout. Thus with the known circuit an optimal DC-offset reduction can only be accomplished if the switching frequency is low. In that case the noise reduction is not optimal. On the other hand an optimal noise reduction is accomplished if the switching frequency is high. In that case however the DC-offset reduction is not optimal. Thus, with the known circuit, an optimal DC-offset reduction and an optimal noise reduction can not be accomplished at the same time.